As a top plate for a cooking device such as an electromagnetic heating cooking device, an infrared heating cooking device, or a gas cooking device, there exists a top plate including a glass sheet. On the glass sheet, a light-shielding film made of a metal, e.g., Ti is formed. The light-shielding film visually shields a heater or the like arranged inside the cooking device, thereby providing good appearance to the cooking device.
In recent years, a top plate including a touch panel having a surface of the glass sheet as a touch surface has been manufactured for the purpose of improving convenience of the cooking device. This kind of top plate requires enhanced insulating properties by reducing electrical conductivity of the light-shielding film formed on the glass. Therefore, a light-shielding film made of a semiconductor is formed on the glass sheet in some cases in place of the light-shielding film made of a metal.
An example of such a top plate is disclosed in Patent Literature 1. In the top plate for a cooking device disclosed in Patent Literature 1, a light-shielding film made of Si being a semiconductor is formed on the glass sheet. As a result, as compared to the light-shielding film made of a metal, the insulating properties can be enhanced.